CN109873163B - A current collector, its pole piece and battery and application - Google Patents

Abstract

The present application relates to the field of batteries, in particular, to a current collector, its pole piece, batteries and applications. The current collector of the present application includes an insulating layer with supporting function and a conductive layer with conductive and current collecting functions, and the normal temperature sheet resistance R _S of the conductive layer satisfies: 0.01Ω/□≦R _S ≦0.15Ω/□. The current collector can greatly improve the short-circuit resistance when the battery is short-circuited under abnormal conditions, so that the short-circuit current can be greatly reduced, so it can greatly reduce the short-circuit heat generation and greatly improve the safety performance of the battery; The heat generated at the site where the internal short circuit occurs can be completely absorbed by the battery, and the temperature rise caused to the battery is also small, so that the impact of the short-circuit damage on the battery can be limited to the "point" range, and only a "point open circuit" is formed. It does not affect the normal operation of the battery in a short period of time.

Description

A current collector, its pole piece and battery and application

technical field

The present application relates to the field of batteries, in particular, to a current collector, its pole piece, batteries and applications.

Background technique

Lithium-ion batteries are widely used in electric vehicles and consumer electronic products due to their advantages of high energy density, high output power, long cycle life and low environmental pollution. However, lithium-ion batteries are prone to fire and explode when subjected to abnormal conditions such as extrusion, collision or puncture, causing serious harm. Therefore, the safety problem of lithium-ion batteries limits the application and popularization of lithium-ion batteries to a great extent.

A large number of experimental results show that the short circuit in the battery is the root cause of the safety hazard of lithium-ion batteries. In order to avoid the occurrence of short circuit in the battery, researchers have tried to improve the structure of the separator and the mechanical structure of the battery. Some of these studies are aimed at improving the safety performance of lithium-ion batteries by improving the design of current collectors.

When an internal short circuit occurs in the battery due to abnormal conditions such as collision, extrusion, puncture, etc., the battery temperature will rise; in the prior art, there is a technical solution of adding a low melting point alloy to the material of the metal current collector. As the current rises, the low melting point alloy in the current collector is melted, causing the pole piece to open circuit, thereby cutting off the current, thereby improving the safety of the battery; or using a multi-layer structure current collector with a resin layer and a metal layer on both sides As the battery temperature rises, when the melting point of the resin layer material is reached, the resin layer of the current collector melts and the pole piece is damaged, thereby cutting off the current, thereby improving the safety of the battery.

However, none of these methods in the prior art can effectively prevent the occurrence of a short circuit in the lithium ion battery, and also cannot guarantee that the battery can continue to work after an abnormal situation occurs. In the above improved methods, the temperature of the battery will still rise sharply after the internal short circuit occurs in the battery. When the temperature of the battery rises sharply, if the safety component cannot respond quickly, there will still be dangers to varying degrees; and in the above improvements In the method, after the safety component responds, although the safety hazard of the battery is solved, the battery cannot continue to work.

Therefore, it is necessary to provide a current collector and a battery design that can effectively prevent accidents such as fire and explosion caused by the occurrence of internal short circuits in the battery after collision, extrusion, puncture, etc., without affecting the normal operation of the battery. .

SUMMARY OF THE INVENTION

In view of this, the present application proposes a current collector, its pole piece, battery and application.

In a first aspect, the present application proposes a current collector; comprising an insulating layer and a conductive layer, the insulating layer is used for supporting the conductive layer; the conductive layer is used for supporting the electrode active material layer, and the conductive layer is located in the On at least one surface of the insulating layer, the normal temperature sheet resistance R _S of the conductive layer satisfies: 0.01Ω/□≦R _S ≦0.15Ω/□.

In the second aspect, the present application proposes the application of the current collector in preparing a battery that only forms a point disconnection for self-protection when subjected to an abnormal situation that causes a short circuit.

In a third aspect, the present application proposes the use of the current collector as a current collector for a battery that only forms a point disconnection when subjected to an abnormal situation that causes a short circuit.

In a fourth aspect, the present application provides a pole piece including the current collector of the first aspect.

In a fifth aspect, the present application provides a battery including the pole piece of the fourth aspect.

The technical solution of the present application has at least the following beneficial effects:

The present application proposes a current collector, the current collector includes an insulating layer with supporting function and a conductive layer with conductive and current collecting functions, and the normal temperature sheet resistance R _S of the conductive layer satisfies: 0.01Ω/□≤R _S ≤0.15Ω/ □. The current collector can greatly improve the short-circuit resistance when the battery is short-circuited under abnormal conditions, so that the short-circuit current can be greatly reduced, so it can greatly reduce the short-circuit heat generation and greatly improve the safety performance of the battery; The heat generated at the site where the internal short circuit occurs can be completely absorbed by the battery, and the temperature rise caused to the battery is also small, so that the impact of the short-circuit damage on the battery can be limited to the "point" range, and only a "point open circuit" is formed. It does not affect the normal operation of the battery in a short period of time. The conductive layer of the current collector of the present application may further include a conductive layer body and a protective layer on at least one surface of the conductive layer body, so that the working stability and service life of the current collector can be greatly improved.

Moreover, the battery with the current collector can be damaged by multiple internal short circuits at the same time or in succession, all accidents such as fire and explosion will not occur, and all can work normally in a short period of time. In addition, the current collector with the normal temperature sheet resistance of the conductive layer in the above range not only has excellent safety performance, but also enables the battery to have good electrochemical performance such as discharge capacity and rate performance.

Description of drawings

1 is a schematic structural diagram of a positive electrode current collector according to a specific embodiment of the present application;

2 is a schematic structural diagram of a positive electrode current collector according to another specific embodiment of the present application;

3 is a schematic structural diagram of a negative electrode current collector according to a specific embodiment of the present application;

4 is a schematic structural diagram of a negative electrode current collector according to another specific embodiment of the present application;

5 is a schematic structural diagram of a positive electrode current collector according to another specific embodiment of the present application;

6 is a schematic structural diagram of a positive electrode current collector according to another specific embodiment of the present application;

7 is a schematic structural diagram of a positive electrode current collector according to another specific embodiment of the present application;

8 is a schematic structural diagram of a positive electrode current collector according to another specific embodiment of the present application;

9 is a schematic structural diagram of a positive electrode current collector according to another specific embodiment of the present application;

10 is a schematic structural diagram of a negative electrode current collector according to another specific embodiment of the present application;

11 is a schematic structural diagram of a negative electrode current collector according to another specific embodiment of the present application;

12 is a schematic structural diagram of a negative electrode current collector according to another specific embodiment of the present application;

13 is a schematic structural diagram of a negative electrode current collector according to another specific embodiment of the present application;

14 is a schematic structural diagram of a negative electrode current collector according to another specific embodiment of the present application;

15 is a schematic structural diagram of a negative electrode current collector according to another specific embodiment of the present application;

16 is a schematic structural diagram of a negative electrode current collector according to another specific embodiment of the present application;

17 is a schematic structural diagram of a positive electrode piece according to a specific embodiment of the present application;

18 is a schematic structural diagram of a positive electrode piece according to another specific embodiment of the present application;

19 is a schematic structural diagram of a negative pole piece according to a specific embodiment of the application;

20 is a schematic structural diagram of a negative pole piece according to another specific embodiment of the application;

Figure 21 is a schematic diagram of a nail penetration experiment of the application;

Figure 22 is the temperature change curve of battery 1# and battery 4# after a nail penetration test;

Figure 23 is the voltage change curve of battery 1# and battery 4# after a nail penetration test;

in:

1- positive pole piece;

10- positive current collector;

101- positive insulating layer;

102-anode conductive layer;

1021- positive electrode conductive layer body;

1022 - positive electrode protective layer;

11- positive electrode active material layer;

2- negative pole piece;

20- negative electrode current collector;

201-negative insulating layer;

202- negative electrode conductive layer;

2021-The body of the negative electrode conductive layer;

2022-Anode protective layer;

21- negative electrode active material layer;

3-diaphragm;

4- Nails.

Detailed ways

The present application will be further described below with reference to specific embodiments. It should be understood that these examples are only used to illustrate the present application and not to limit the scope of the present application.

Embodiments of the present application provide a current collector including an insulating layer and a conductive layer. The insulating layer is used to carry the conductive layer, which supports and protects the conductive layer; the conductive layer is used to carry the electrode active material layer, and is used to provide electrons for the electrode active material layer, that is, it plays the role of conduction and current collection; The layer is on at least one surface of the insulating layer.

FIG. 1 and FIG. 2 are schematic diagrams of the structure of the positive electrode current collector according to the embodiment of the present application. As shown in FIG. 1 and FIG. 2 , the positive electrode current collector 10 includes a positive electrode insulating layer 101 and a positive electrode conductive layer 102, which are used for coating positive electrode active materials to prepare Positive pole piece. 3 and 4 are schematic structural diagrams of the negative electrode current collectors according to the embodiments of the present application. As shown in FIGS. 3 and 4 , the negative electrode current collector 20 includes a negative electrode insulating layer 201 and a negative electrode conductive layer 202, which are used for coating negative electrode active materials to prepare Negative pole piece. Wherein, as shown in FIG. 1 and FIG. 3 , conductive layers may be provided on two opposite surfaces of the insulating layer. As shown in FIG. 2 and FIG. 4 , conductive layers may also be provided on only one side of the insulating layer. .

The structures and properties of the current collectors of the embodiments of the present application will be described in detail below.

[Conductive layer]

In the current collector of the embodiment of the present application, the sheet resistance R _S of the conductive layer at room temperature satisfies: 0.01Ω/□≦R _S ≦0.15Ω/□.

Among them, the sheet resistance of the conductive layer is measured in ohms/square (Ω/□), which can be applied to a two-dimensional system considering a conductor as a two-dimensional entity, which is equivalent to the concept of resistivity used in a three-dimensional system . When the concept of sheet resistance is used, current is theoretically assumed to flow along the plane of the film.

For conventional three-dimensional conductors, the formula for calculating resistance is:

Among them, ρ is the resistivity, A is the cross-sectional area, and L is the length. The cross-sectional area can be decomposed into the width W and the film thickness t, that is, the resistance can be written as:

Among them, R _S is the thin film resistance. When the diaphragm is square, L=W, the measured resistance R is the sheet resistance R _S of the diaphragm, and R _S has nothing to do with the size of L or W, R _S is the resistance value of the unit square, so R _S The unit can be expressed as ohms per square (Ω/□).

The room temperature thin film resistance in the embodiments of the present application refers to the resistance value measured by the four-probe method on the conductive layer under normal temperature conditions, wherein the normal temperature refers to 15°C to 25°C.

In the existing lithium-ion battery, when a short circuit occurs in the battery under abnormal conditions, a large current is generated instantaneously, and a large amount of short circuit heat is generated. This can cause the battery to catch fire or explode. In the embodiments of the present application, the above-mentioned technical problems are solved by increasing the normal temperature sheet resistance R _S of the current collector.

The internal resistance of the battery usually includes the battery ohmic internal resistance and the battery polarization internal resistance, among which the active material resistance, current collector resistance, interface resistance, and electrolyte composition will all have a significant impact on the internal resistance of the battery.

When a short circuit occurs under abnormal conditions, the internal resistance of the battery will be greatly reduced due to the occurrence of an internal short circuit. Therefore, increasing the resistance of the current collector can increase the internal resistance of the battery after short circuit, thereby improving the safety performance of the battery. In the embodiment of the present application, when the battery can limit the impact of short-circuit damage on the battery to the "point" range, the impact of short-circuit damage on the battery can be limited to the damage point, and the high resistance of the current collector makes the short-circuit current It is greatly reduced, and the short-circuit heat generation makes the temperature rise of the battery not obvious, and does not affect the normal use of the battery in a short period of time, which is called "point circuit breaker".

When the sheet resistance R _S of the conductive layer at room temperature satisfies: 0.01Ω/□≤R _S ≤0.15Ω/□, the short-circuit current can be greatly reduced in the case of an internal short circuit of the battery, so the short-circuit heat generation can be greatly reduced , greatly improving the safety performance of the battery; in addition, the short-circuit heat generation can also be controlled within the range that the battery can fully absorb, so the heat generated at the site where the internal short-circuit occurs can be completely absorbed by the battery. It is also very small, so that the impact of short-circuit damage on the battery can be limited to the "point" range, and only a "point open circuit" is formed, without affecting the normal operation of the battery in a short period of time.

Optionally, the normal temperature sheet resistance R _S of the conductive layer satisfies: 0.02Ω/□≤R _S ≤0.1Ω/□.

When the normal temperature sheet resistance R _S of the conductive layer is too large, it will affect the conduction and current collection functions of the conductive layer, and electrons cannot be effectively conducted between the current collector, the electrode active material layer and the interface between the two, that is, the increase in The polarization of the electrode active material layer on the surface of the large conductive layer affects the electrochemical performance of the battery such as discharge capacity and rate performance. Therefore, the normal temperature sheet resistance R _S of the conductive layer satisfies: 0.01Ω/□≦R _S ≦0.15Ω/□.

In this application, the upper limit of the sheet resistance R _S at room temperature may be 0.15Ω/□, 0.12Ω/□, 0.1Ω/□, 0.09Ω/□, 0.08Ω/□, 0.07Ω/□, 0.05Ω/□, at room temperature The lower limit of the sheet resistance R _S can be 0.01Ω/□, 0.02Ω/□, 0.025Ω/□, 0.03Ω/□, 0.04Ω/□; the range of the normal temperature sheet resistance R _S can be composed of any value of the upper limit or the lower limit.

In addition, the thickness of the conductive layer also has a great influence on the working reliability and working life of the current collector according to the present application.

Preferably, in the current collector of the embodiment of the present application, the thickness of the conductive layer is D2, and D2 satisfies: 300nm≤D2≤2μm. If the conductive layer is too thin, although it is beneficial to increase the normal temperature sheet resistance R _S of the current collector, it is easy to be damaged in the process of pole piece processing; if the conductive layer is too thick, it will affect the weight energy density of the battery. And it will be disadvantageous to increase the normal temperature sheet resistance R _S of the conductive layer.

The upper limit of the thickness D2 of the conductive layer can be 2 μm, 1.8 μm, 1.5 μm, 1.2 μm, 1 μm, 900 nm, 800 nm, 700 nm, 600 nm, 500 nm, and the lower limit of the thickness D2 of the conductive layer can be 300 nm, 350 nm, 400 nm, 450 nm ; The range of the thickness D2 of the conductive layer can be composed of any numerical value of the upper limit or the lower limit. Preferably, 500 nm≤D2≤1.5 μm.

Optionally, the material of the conductive layer is selected from at least one of metal conductive materials and carbon-based conductive materials. Among them, the metal conductive material is preferably at least one of aluminum, copper, nickel, titanium, silver, nickel-copper alloy, and aluminum-zirconium alloy; the carbon-based conductive material is preferably at least one of graphite, acetylene black, graphene, and carbon nanotubes. .

The conductive layer can be formed on the insulating layer by at least one of mechanical rolling, bonding, vapor deposition, and electroless plating. The vapor deposition method is preferably physical vapor deposition. , PVD); physical vapor deposition method is preferably at least one of evaporation method and sputtering method; evaporation method is preferably vacuum evaporation method (vacuum evaporating), thermal evaporation method (Thermal Evaporation Deposition), electron beam evaporation method (electron beam evaporation method) , EBEM) at least one, the sputtering method is preferably a magnetron sputtering method (Magnetron sputtering).

Further, the conductive layer of the current collector in the embodiment of the present application may include a conductive layer body and a protective layer located on at least one surface of the conductive layer body. The protective layer can prevent the body of the conductive layer from being oxidized, corroded or destroyed, thereby greatly improving the working stability and service life of the current collector.

5 to 12 are schematic structural diagrams of a current collector provided with a protective layer according to an embodiment of the present application. The schematic diagrams of the positive electrode current collectors are shown in FIGS. 5 to 10 .

In FIG. 5 , the positive electrode current collector 10 includes a positive electrode insulating layer 101 and a positive electrode conductive layer 102 disposed on two opposite surfaces of the positive electrode insulating layer 101 , and the positive electrode conductive layer 102 includes a positive electrode conductive layer body 1021 and is provided on the positive electrode conductive layer body. 1021 is the positive electrode protective layer 1022 on the side facing away from the positive electrode insulating layer 101 (ie, the upper surface of the positive electrode conductive layer body 1021).

In FIG. 6 , the positive electrode current collector 10 includes a positive electrode insulating layer 101 and a positive electrode conductive layer 102 disposed on two opposite surfaces of the positive electrode insulating layer 101 , and the positive electrode conductive layer 102 includes a positive electrode conductive layer body 1021 and is provided on the positive electrode conductive layer body. The positive electrode protective layer 1022 on the surface of the 1021 facing the positive electrode insulating layer 101 (ie, the lower surface of the positive electrode conductive layer body 1021 ).

In FIG. 7 , the positive electrode current collector 10 includes a positive electrode insulating layer 101 and a positive electrode conductive layer 102 disposed on two opposite surfaces of the positive electrode insulating layer 101 , and the positive electrode conductive layer 102 includes a positive electrode conductive layer body 1021 and is provided on the positive electrode conductive layer body. The positive electrode protective layer 1022 on the opposite two surfaces of the 1021 (ie, the upper surface and the lower surface of the positive electrode conductive layer body 1021 ).

In FIG. 8 , the positive electrode current collector 10 includes a positive electrode insulating layer 101 and a positive electrode conductive layer 102 disposed on one surface of the positive electrode insulating layer 101 , and the positive electrode conductive layer 102 includes a positive electrode conductive layer body 1021 and a positive electrode conductive layer body. The positive electrode protective layer 1022 on the surface of the positive electrode insulating layer 101 (ie, the upper surface of the positive electrode conductive layer body 1021 ).

In FIG. 9 , the positive electrode current collector 10 includes a positive electrode insulating layer 101 and a positive electrode conductive layer 102 disposed on one surface of the positive electrode insulating layer 101 , and the positive electrode conductive layer 102 includes a positive electrode conductive layer body 1021 and is disposed on the positive electrode conductive layer body 1021. The positive electrode protective layer 1022 on one side of the positive electrode insulating layer 101 (ie, the lower surface of the positive electrode conductive layer body 1021 ).

In FIG. 10 , the positive electrode current collector 10 includes a positive electrode insulating layer 101 and a positive electrode conductive layer 102 disposed on one surface of the positive electrode insulating layer. A positive electrode protective layer 1022 on each surface (ie, the upper and lower surfaces of the positive electrode conductive layer body 1021 ).

Likewise, schematic diagrams of the negative electrode current collectors are shown in FIGS. 11 to 16 .

In FIG. 11 , the negative electrode current collector 20 includes a negative electrode insulating layer 201 and a negative electrode conductive layer 202 provided on two opposite surfaces of the negative electrode insulating layer 201 , and the negative electrode conductive layer 202 includes a negative electrode conductive layer body 2021 and is provided on the negative electrode conductive layer body. The negative electrode protective layer 2022 on the side of the 2021 facing away from the negative electrode insulating layer 201 (ie, the upper surface of the negative electrode conductive layer body 2021 ).

In FIG. 12 , the negative electrode current collector 20 includes a negative electrode insulating layer 201 and a negative electrode conductive layer 202 provided on two opposite surfaces of the negative electrode insulating layer 201 , and the negative electrode conductive layer 202 includes a negative electrode conductive layer body 2021 and is provided on the negative electrode conductive layer body. The negative electrode protective layer 2022 on the surface of the 2021 facing the negative electrode insulating layer 201 (ie, the lower surface of the negative electrode conductive layer body 2021 ).

In FIG. 13 , the negative electrode current collector 20 includes a negative electrode insulating layer 201 and a negative electrode conductive layer 202 provided on two opposite surfaces of the negative electrode insulating layer 201 , and the negative electrode conductive layer 202 includes a negative electrode conductive layer body 2021 and is provided on the negative electrode conductive layer body. The negative electrode protective layer 2022 on the opposite two surfaces of the 2021 (ie, the upper surface and the lower surface of the negative electrode conductive layer body 2021).

In FIG. 14 , the negative electrode current collector 20 includes a negative electrode insulating layer 201 and a negative electrode conductive layer 202 provided on one surface of the negative electrode insulating layer 201 , and the negative electrode conductive layer 202 includes a negative electrode conductive layer body 2021 and a negative electrode conductive layer body. The negative electrode protective layer 2022 on the surface of the negative electrode insulating layer 201 (ie, the upper surface of the negative electrode conductive layer body 2021 ).

In FIG. 15 , the negative electrode current collector 20 includes a negative electrode insulating layer 201 and a negative electrode conductive layer 202 disposed on one surface of the negative electrode insulating layer 201 . The negative electrode conductive layer 202 includes a negative electrode conductive layer body 2021 and a direction of the negative electrode conductive layer body 2021 . The negative electrode protective layer 2022 on the face of the negative electrode insulating layer 201 (ie, the lower surface of the negative electrode conductive layer body 2021 ).

In FIG. 16 , the negative electrode current collector 20 includes a negative electrode insulating layer 201 and a negative electrode conductive layer 202 disposed on one surface of the negative electrode insulating layer 201 , and the negative electrode conductive layer 202 includes a negative electrode conductive layer body 2021 and an opposite electrode disposed on the negative electrode conductive layer body 2021 . The negative electrode protective layer 2022 on both surfaces (ie, the upper surface and the lower surface of the negative electrode conductive layer body 2021).

Optionally, the protective layer is located on the lower surface of the conductive layer body, that is, between the conductive layer body and the insulating layer. The protective layer located at this position can not only protect the conductive layer body, thereby improving the life and working reliability of the current collector, but also have the following advantages: (1) Compared with the protective layer located on the upper surface of the conductive layer body, the conductive layer is located in the conductive layer. The bonding force between the protective layer on the lower surface of the body and the body of the conductive layer is stronger, and can better protect the body of the conductive layer; (2) the protective layer on the lower surface of the body of the conductive layer can better enhance the current collector (3) The protective layer on the lower surface of the conductive layer body can form a complete supporting structure to protect the conductive layer body.

Optionally, the protective layer is located on two opposite surfaces of the conductive layer body, that is, the upper surface and the lower surface of the conductive layer body, so as to maximize the working stability and service life of the current collector and improve the battery life. Capacity retention rate, cycle life and other performance.

Wherein, the material of the conductive layer body is selected from at least one of metal conductive materials and carbon-based conductive materials. The metal conductive material can be selected from at least one of aluminum, copper, nickel, titanium, silver, nickel-copper alloy, and aluminum-zirconium alloy, and the carbon-based conductive material can be selected from graphite, acetylene black, graphene, carbon nanomaterials at least one of the tubes.

The material of the protective layer can be selected from at least one of metals, metal oxides, and conductive carbon. Optionally, the metal is selected from at least one of nickel, chromium, nickel-based alloys (such as nickel-chromium alloys), and copper-based alloys (such as copper-nickel alloys); optionally, the metal oxides are selected from aluminum oxide, cobalt oxide , at least one of chromium oxide, and nickel oxide; optionally, the conductive carbon is selected from at least one of conductive carbon black, carbon nanotubes, acetylene black, and graphene.

Among them, the nickel-based alloy is an alloy composed of pure nickel as the matrix and one or several other elements added. It is preferably a nickel-chromium alloy, and the nickel-chromium alloy is an alloy formed by metal nickel and metal chromium. Optionally, the molar ratio of nickel element to chromium element is 1:99-99:1.

Copper-based alloys are alloys formed by adding one or several other elements to the base of pure copper. It is preferably a copper-nickel alloy. Optionally, in the copper-nickel alloy, the molar ratio of nickel element to copper element is 1:99-99:1.

The materials of the protective layers on the two opposite surfaces of the conductive layer body may be the same or different, and the thicknesses may be the same or different.

The thickness of the protective layer is D3, and when D3≤1/10D2, the influence of the protective layer on the normal temperature sheet resistance of the conductive layer can be ignored.

As a further improvement of the current collector in the embodiment of the present application, the thickness of the protective layer is D3, and D3 satisfies: D3≤1/10D2 and 1nm≤D3≤200nm, that is, the thickness satisfies 1/10 or less of the thickness of D2 in the range of 1nm～200nm . Wherein, the upper limit of the thickness D3 of the protective layer can be 200nm, 180nm, 150nm, 120nm, 100nm, 80nm, 60nm, 55nm, 50nm, 45nm, 40nm, 30nm, 20nm, and the lower limit of the thickness D3 of the protective layer can be 1nm, 2nm, 5nm, 8nm, 10nm, 12nm, 15nm, 18nm; the range of the thickness D3 of the protective layer can be composed of any numerical value of the upper limit or the lower limit. If the protective layer is too thin, it will not be enough to protect the conductive layer; if the protective layer is too thick, the weight energy density and volume energy density of the battery will be reduced. Preferably, 10nm≤D3≤50nm.

From the perspective of the thickness of the protective layer accounting for the entire conductive layer, preferably, D3 satisfies: 1/2000D2≤D3≤1/10D2, that is, the thickness is 1/2000-1/10 of D2. More preferably, D3 satisfies: 1/1000D2≤D3≤1/10D2.

The protective layer may be formed on the conductive layer body by a vapor deposition method, an in-situ formation method, a coating method, or the like. The vapor deposition method is preferably a physical vapor deposition method (Physical Vapor Deposition, PVD); the physical vapor deposition method is preferably at least one of an evaporation method and a sputtering method; At least one of Deposition) and electron beam evaporation method (electron beam evaporation method, EBEM), the sputtering method is preferably magnetron sputtering (Magnetron sputtering). The in-situ formation method is preferably an in-situ passivation method, that is, a method in which a metal oxide passivation layer is formed in-situ on a metal surface. The coating method is preferably one of roll coating, extrusion coating, blade coating, gravure coating, and the like.

[Insulation]

In the current collector of the embodiment of the present application, the insulating layer mainly plays the role of supporting and protecting the conductive layer, and its thickness is D1, and D1 satisfies 1 μm≤D1≤20 μm. If the insulating layer is too thin, it is easy to break during the pole piece processing process, etc.; if it is too thick, it will reduce the volume energy density of the battery using the current collector.

Wherein, the upper limit of the thickness D1 of the insulating layer can be 20 μm, 15 μm, 12 μm, 10 μm, 8 μm, and the lower limit of the thickness D1 of the conductive layer can be 1 μm, 1.5 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm; The range of the thickness D1 may be composed of any numerical value of the upper limit or the lower limit. Preferably, 2 μm≦D1≦10 μm, and more preferably 2 μm≦D1≦6 μm.

Optionally, the material of the insulating layer is selected from one of organic polymer insulating materials, inorganic insulating materials, and composite materials. Further preferably, the composite material is composed of an organic polymer insulating material and an inorganic insulating material.

The organic polymer insulating material is selected from polyamide (Polyamide, referred to as PA), polyethylene terephthalate (Polyethylene terephthalate, referred to as PET), polyimide (Polyimide, referred to as PI), polyethylene (Polyethylene, referred to as PI) PE), Polypropylene (PP), Polystyrene (PS), Polyvinyl chloride (PVC), Acrylonitrile butadiene styrene copolymers, Abbreviated as ABS), polybutylene terephthalate (Polybutylene terephthalat, referred to as PBT), poly-p-phenyleneterephthamide (Poly-p-phenyleneterephthamide, referred to as PPA), epoxy resin (epoxy resin), Polypropylene (PPE for short), Polyformaldehyde (POM), Phenol-formaldehyde resin, Polytetrafluoroethylene (PTFE), Silicone rubber, Polyvinylidenefluoride, At least one of PVDF for short) and Polycarbonate (PC for short).

The inorganic insulating material is preferably at least one of aluminum oxide (Al ₂ O ₃ ), silicon carbide (SiC), and silicon dioxide (SiO ₂ );

The composite is preferably at least one of epoxy resin glass fiber reinforced composite material and polyester resin glass fiber reinforced composite material.

Since the density of the insulating layer is generally smaller than that of the metal, the current collector of the present application can improve the safety performance of the battery while also improving the weight energy density of the battery. And because the insulating layer can have a good bearing and protection effect on the conductive layer located on its surface, it is not easy to produce the phenomenon of pole piece fracture common in traditional current collectors.

A second aspect of the embodiments of the present application provides a pole piece including the current collector of the first aspect of the embodiments of the present application and an electrode active material layer formed on the surface of the current collector.

17 and 18 are schematic diagrams of the structure of the positive electrode sheet according to the embodiment of the present application. As shown in FIGS. 17 and 18 , the positive electrode sheet 1 includes the positive electrode current collector 10 of the present application and a positive electrode active material layer formed on the surface of the positive electrode current collector 10 11. The positive electrode current collector 10 includes a positive electrode insulating layer 101 and a positive electrode conductive layer 102 .

19 and FIG. 20 are schematic views of the structure of the negative electrode pole piece according to the embodiment of the present application. As shown in FIG. 19 and FIG. 20 , the negative electrode pole piece 2 includes the negative electrode current collector 20 of the present application and the negative electrode active material layer formed on the surface of the negative electrode current collector 20 21. The negative electrode current collector 20 includes a negative electrode insulating layer 201 and a negative electrode conductive layer 202 .

Among them, when the insulating layer is provided with a conductive layer on both sides, and the current collector is coated with active material on both sides, the prepared positive electrode and negative electrode are shown in Figure 17 and Figure 19 respectively, which can be directly used in batteries. When a conductive layer is provided on one side of the insulating layer, the active material is coated on one side of the current collector, and the prepared positive electrode and negative electrode are shown in Figure 18 and Figure 20, respectively, which can be folded and used in batteries.

A third aspect of the embodiments of the present application provides a battery including a positive electrode sheet, a separator, a negative electrode sheet and an electrolyte.

Wherein, the positive pole piece and/or the negative pole piece are the pole pieces of the above embodiments of the present application. The battery of the present application may be of a wound type or a laminated type. The battery of the present application may be one of a lithium ion secondary battery, a lithium primary battery, a sodium ion battery, and a magnesium ion battery. But not limited to this.

Further, an embodiment of the present application further provides a battery, including a positive electrode piece, a separator, a negative electrode piece and an electrolyte, and only the positive electrode piece is the positive electrode piece in the above embodiment.

Preferably, the positive pole piece of the battery of the embodiment of the present application adopts the above-mentioned pole piece of the present application. Because the aluminum content in the conventional positive electrode current collector is high, when a short circuit occurs in the abnormal condition of the battery, the heat generated at the short circuit point can cause a violent aluminothermic reaction, thereby generating a large amount of heat and causing accidents such as battery explosion. When the positive electrode plate of the present application is used, since the amount of aluminum in the positive electrode current collector is greatly reduced, the aluminothermic reaction can be avoided, thereby significantly improving the safety performance of the battery.

Next, the abnormal condition of the battery is simulated by using the nail penetration experiment to observe the changes of the battery after nail penetration. FIG. 21 is a schematic diagram of a battery piercing experiment once in an embodiment of the present application. For the sake of simplicity, the figure only shows the situation where the nail 4 penetrates one layer of positive pole piece 1 , one layer of separator 3 and one layer of negative pole piece 2 of the battery. It should be noted that, in the actual nail penetration experiment, the nail 4 penetrates the entire battery, which usually includes a multi-layer positive electrode plate 1 , a multi-layer separator 3 and a multi-layer negative electrode electrode plate 2 . According to Figure 21, when the battery is short-circuited due to the piercing nail, the short-circuit current is greatly reduced, and the short-circuit heat generation is controlled within the range that the battery can fully absorb, so the heat generated at the site where the internal short-circuit occurs can be completely absorbed by the battery. , the temperature rise caused to the battery is also small, so that the impact of short-circuit damage on the battery can be limited to the piercing site, and only a "point break" is formed, without affecting the normal operation of the battery in a short period of time.

In addition, this application has found through a large number of experiments that the larger the capacity of the battery, the smaller the internal resistance of the battery, the worse the safety performance of the battery, that is, the battery capacity (Cap) and the battery internal resistance (r) are inversely proportional:

r=A/Cap

In the formula, r represents the internal resistance of the battery, Cap represents the capacity of the battery, and A is the coefficient.

The battery capacity Cap is the theoretical capacity of the battery, usually the theoretical capacity of the positive electrode plate of the battery.

r can be obtained through the internal resistance test.

For conventional lithium-ion secondary batteries composed of conventional positive electrode and conventional negative electrode, due to the occurrence of internal short-circuit under abnormal conditions, almost all conventional lithium-ion secondary batteries will experience varying degrees of smoke, Fire, explosion, etc.

However, for the battery of the embodiment of the present application, since the battery has a relatively large internal resistance under the condition of the same battery capacity, it can have a relatively large A value.

For the batteries of the embodiments of the present application, when the coefficient A satisfies 25Ah·mΩ≤A≤400Ah·mΩ, the batteries can have both good electrochemical performance and good safety performance.

When the A value is too large, the electrochemical performance of the battery will be deteriorated due to excessive internal resistance, so it is not practical.

When the A value is too small, the temperature rise of the battery is too high when an internal short circuit occurs, and the safety performance of the battery is reduced.

More preferably, the coefficient A satisfies 30Ah·mΩ≤A≤200Ah·mΩ; more preferably, the coefficient A satisfies 40Ah·mΩ≤A≤150Ah·mΩ.

The embodiments of the present application also relate to the application of the current collector in preparing a battery that only forms a point disconnection for self-protection when subjected to an abnormal situation that causes a short circuit. In this application, when the battery can limit the impact of short-circuit damage on the battery to the "point" range, and does not affect the normal use of the battery in a short period of time, it is called "point open circuit".

On the other hand, the embodiments of the present application also relate to the use of the current collector as a current collector of a battery that only forms a point disconnection when subjected to an abnormal condition that causes a short circuit.

Preferably, the abnormal conditions that cause the short circuit include impact, extrusion, foreign object piercing, etc. Since the short circuit caused by these damage processes is caused by the electrical connection of the positive and negative electrodes with materials with certain conductivity, so in this application These abnormal conditions are collectively referred to as piercing. And in the specific embodiment of the present application, the abnormal situation of the battery is simulated through the nail penetration experiment.

Example

1. Preparation of current collector:

Select an insulating layer of a certain thickness, form a conductive layer of a certain thickness on its surface by vacuum evaporation, mechanical rolling or bonding, and measure the normal temperature sheet resistance of the conductive layer.

in,

(1) The formation conditions of the vacuum evaporation method are as follows: place the insulating layer after surface cleaning treatment in the vacuum plating chamber, melt and evaporate the high-purity metal wire in the metal evaporation chamber at a high temperature of 1600 ℃ to 2000 ℃, and the evaporated metal After passing through the cooling system in the vacuum plating chamber, it is finally deposited on the surface of the insulating layer to form a conductive layer.

(2) The forming conditions of the mechanical rolling method are as follows: the foil of the conductive layer material is placed in a mechanical roller, rolled to a predetermined thickness by applying a pressure of 20t to 40t, and then placed in a surface cleaning treatment The surface of the insulating layer is finally placed in a mechanical roller, and the two are tightly combined by applying a pressure of 30t to 50t.

(3) The forming conditions of the bonding method are as follows: the foil of the conductive layer material is placed in a mechanical roller, and it is rolled to a predetermined thickness by applying a pressure of 20t to 40t; The surface is coated with a mixed solution of PVDF and NMP; finally, the above-mentioned conductive layer with a predetermined thickness is bonded to the surface of the insulating layer, and dried at 100°C.

(4) The method for measuring thin film resistance at room temperature is:

Use RTS-9 double-electrical four-probe tester, the test environment is: normal temperature 23 ± 2 ℃, relative humidity ≤ 65%. During the test, clean the surface of the material to be tested, then place it horizontally on the test bench, put down the four probes to make the probes have good contact with the surface of the material to be tested, and then adjust the current range of the material to be calibrated in the automatic test mode. The thin-film square resistance measurement was carried out under the current range of 100, and 8 to 10 data points of the same sample were collected as the data measurement accuracy and error analysis.

The specific parameters of the current collectors and their pole pieces of the examples and comparative examples of the present application are shown in Table 1.

2. Preparation of current collector with protective layer:

There are several ways to prepare a current collector with a protective layer:

(1) First, a protective layer is provided on the surface of the insulating layer by vapor deposition method or coating method, and then a conductive layer of a certain thickness is formed on the surface of the insulating layer with a protective layer by vacuum evaporation, mechanical rolling or bonding. body to prepare a current collector with a protective layer (the protective layer is located between the insulating layer and the conductive layer body); in addition, on the basis of the above, vapor deposition method, In-situ formation method or coating method forms another protective layer to prepare a current collector with protective layer (the protective layer is located on two opposite surfaces of the conductive layer body);

(2) First, a protective layer is formed on one surface of the conductive layer body by a vapor deposition method, an in-situ formation method or a coating method, and then the above-mentioned conductive layer body with a protective layer is arranged by mechanical rolling or bonding. on the surface of the insulating layer, and the protective layer is arranged between the insulating layer and the conductive layer body to prepare a current collector with a protective layer (the protective layer is located between the insulating layer and the conductive layer body); in addition, on the basis of the above, Then another protective layer is formed on the surface of the conductive layer body away from the insulating layer by vapor deposition method, in-situ formation method or coating method to prepare a current collector with a protective layer (the protective layer is located on the two sides of the conductive layer body. opposite surface);

(3) First, a protective layer is formed on one surface of the conductive layer body by a vapor deposition method, an in-situ formation method or a coating method, and then the above-mentioned conductive layer body with a protective layer is arranged by mechanical rolling or bonding. on the surface of the insulating layer, and the protective layer is arranged on the surface of the conductive layer body away from the insulating layer to prepare a current collector with a protective layer (the protective layer is located on the surface of the conductive layer body away from the insulating layer);

(4) First, a protective layer is formed on both surfaces of the conductive layer body by a vapor deposition method, an in-situ formation method or a coating method, and then the above-mentioned conductive layer body with a protective layer is formed by mechanical rolling or bonding. arranged on the surface of the insulating layer to prepare a current collector with a protective layer (the protective layer is located on two opposite surfaces of the conductive layer body);

(5) On the basis of the above-mentioned "preparation of current collector", another layer of protective layer is formed on the surface of the conductive layer body away from the direction of the insulating layer by vapor deposition method, in-situ formation method or coating method to prepare A current collector with a protective layer (the protective layer is located on the surface of the conductive layer body facing away from the insulating layer).

In the preparation examples, the vapor deposition method adopts the vacuum evaporation method, the in-situ formation method adopts the in-situ passivation method, and the coating method adopts the blade coating method.

The formation conditions of the vacuum evaporation method are as follows: place the surface-cleaned sample in a vacuum coating chamber, melt and evaporate the protective layer material in the evaporation chamber at a high temperature of 1600 ° C to 2000 ° C, and evaporate the protective layer material through the vacuum coating chamber. The cooling system is finally deposited on the surface of the sample to form a protective layer.

The formation conditions of the in-situ passivation method are as follows: the conductive layer body is placed in a high-temperature oxidizing environment, the temperature is controlled at 160 ° C to 250 ° C, and the oxygen supply is maintained in the high temperature environment at the same time, and the processing time is 30 minutes, thereby forming metal oxides protective layer.

The formation conditions of the gravure coating method are as follows: the protective layer material and NMP are stirred and mixed, and then the slurry of the above protective layer material (solid content is 20% to 75%) is coated on the surface of the sample, and then the coating is controlled by a gravure roll. thickness, and finally dried at 100 °C ~ 130 °C.

The prepared current collector with protective layer and the specific parameters of its pole piece are shown in Table 2.

3. Preparation of pole pieces:

Through a conventional battery coating process, a positive electrode slurry or a negative electrode slurry is coated on the surface of the current collector, and the positive electrode electrode sheet or the negative electrode electrode sheet is obtained after drying at 100°C.

Conventional positive electrode: the current collector is an Al foil with a thickness of 12 μm, and the electrode active material layer is a ternary (NCM) material layer with a certain thickness.

Conventional negative pole piece: the current collector is a Cu foil with a thickness of 8 μm, and the electrode active material layer is a graphite material layer with a certain thickness.

In Table 1, there is no protective layer in the current collectors from pole piece 1# to pole piece 10#; the pole piece in Table 2 is provided with a protective layer, wherein "pole piece 3-1#" represents the body of the conductive layer and the pole piece 3 The conductive layers of # are the same, and so on, "pole piece 6-4#" means that the conductive layer body is the same as the conductive layer of pole piece 6#, and so on.

4. Preparation of battery:

Through the conventional battery manufacturing process, the positive electrode (compacted density: 3.4g/cm ³ ), PP/PE/PP separator and negative electrode (compacted density: 1.6 g/cm ³ ) were wound together to form a bare battery The core is then placed in the battery case, and the electrolyte (EC:EMC volume ratio is 3: ₇ , LiPF6 is 1mol/L) is injected, followed by sealing, chemical formation and other processes, and finally a lithium ion secondary battery is obtained.

Table 3 shows the specific compositions of the batteries prepared in the examples of the present application and the batteries of the comparative example.

Table 1

Table 2:

Among them, the protective layer 1 refers to the protective layer located on the surface of the conductive layer body facing the insulating layer (that is, the lower surface), and its thickness is D3'; the protective layer 2 refers to the surface of the conductive layer body facing away from the insulating layer (that is, the upper surface). ) with a thickness of D3"; "/" means no protective layer.

table 3

Among them, by further increasing the number of winding layers of the battery cells, the battery 12# and the battery 13# with further improved capacity are prepared.

Experimental example:

1. Battery test method:

The cycle life test of lithium-ion battery is carried out, and the specific test method is as follows:

The lithium-ion battery was charged and discharged at two temperatures of 25°C and 45°C, that is, first charged to 4.2V with a current of 1C, and then discharged to 2.8V with a current of 1C, and recorded the discharge capacity of the first week; The battery was then subjected to 1C/1C charge-discharge cycles for 1000 cycles, the battery discharge capacity at the 1000th cycle was recorded, and the 1000th cycle discharge capacity was divided by the first cycle discharge capacity to obtain the 1000th cycle capacity retention rate.

The experimental results are shown in Table 4.

2. Test of battery internal resistance

Use an internal resistance meter (model HIOKI-BT3562) to test, and the test environment is: normal temperature 23±2℃. Before the test, short-circuit the positive and negative ends of the internal resistance meter to calibrate the resistance to zero; during the test, clean the positive and negative electrodes of the lithium-ion battery to be tested, and then connect the positive and negative test ends of the internal resistance meter to the lithium ion battery. The positive and negative tabs of the ion battery are tested and recorded. And calculate the coefficient A according to the formula r=A/Cap.

3. Experimental methods and test methods for one nail penetration experiment and six consecutive nail penetration experiments:

(1) One nail penetration experiment: After the battery is fully charged, it is fixed. At room temperature, a steel needle with a diameter of 6 mm is passed through the battery at a speed of 25 mm/s, and the steel needle is kept in the battery. test.

(2) Six nail penetration experiments: After the battery is fully charged, it is fixed. At room temperature, six steel needles with a diameter of 6 mm are quickly penetrated through the battery at a speed of 25 mm/s, and the steel needles are retained in the battery. Done, then observe and test.

(3) Test of battery temperature: Use a multi-channel thermometer to attach a temperature sensing line to the acupuncture surface and the geometric center of the back of the battery to be pierced. After the piercing is completed, track the battery temperature for five minutes. Test, then record the temperature of the battery for five minutes.

(4) Battery voltage test: Connect the positive and negative electrodes of the battery to be pierced to the measuring end of the internal resistance meter. After the piercing is completed, perform a five-minute battery voltage tracking test, and then record the battery voltage for five minutes. voltage.

The recorded battery temperature and voltage data are shown in Table 5.

Table 4

table 5

Note: "N/A" means that a steel needle penetrates into the battery and thermal runaway and destruction occurs instantaneously.

Table 6

According to the results in Table 4, compared with the battery 1# using the conventional positive electrode plate and the conventional negative electrode plate, the cycle life of the battery using the current collector of the embodiment of the present application is good, and the cycle performance of the conventional battery is good. quite. This shows that the current collectors in the examples of the present application do not have obvious adverse effects on the prepared pole pieces and batteries. Especially for batteries made of current collectors containing a protective layer, the capacity retention rate is further improved, indicating that the reliability of the batteries is better.

In addition, the current collectors of the embodiments of the present application can greatly improve the safety performance of lithium ion batteries. Figure 22 shows the variation curves of battery temperature with time for battery 1# and battery 4#, and Figure 23 shows the variation curves of voltage with time. From the results in Table 5 and FIGS. 22 and 23 , the battery 1 # without the current collector of the embodiment of the present application, at the moment of piercing the nail, the temperature of the battery suddenly rises by several hundred degrees, and the voltage drops to zero, which shows that At the moment when the nail is pierced, the battery has an internal short circuit, which generates a lot of heat, and the battery is thermally out of control and destroyed in an instant, and it cannot continue to work. Therefore, it is impossible to carry out the continuous nail penetration experiment of six steel needles on this type of battery.

However, the lithium ion battery using the current collector of the embodiment of the present application, especially when the current collector of the embodiment of the present application is the positive electrode current collector, no matter whether it is subjected to one nail penetration experiment or six consecutive nail penetration experiments, the temperature rise of the battery is basically the same. It can be controlled at about 10°C or below 10°C, the voltage is basically stable, and the cells can work normally.

The data in Table 6 shows that the increase in the resistance of the current collector is beneficial to increase the internal resistance r of the battery, thereby increasing the value of the coefficient A, thereby improving the safety performance of the battery; especially when the capacity of the battery is large, the resistance of the current collector increases. It can effectively improve the internal resistance r of the battery, so as to keep the value of the coefficient A in a high value range and improve the safety performance of the battery.

It can be seen that in the case of an internal short circuit in the battery, the current collector of the embodiment of the present application can greatly reduce the short-circuit heat generation, thereby improving the safety performance of the battery; in addition, the impact of the short-circuit damage on the battery can be limited to the "point" range , only a "point break" is formed without affecting the normal operation of the battery in a short period of time.

Although the present application is disclosed above with preferred embodiments, it is not used to limit the claims. Any person skilled in the art can make some possible changes and modifications without departing from the concept of the present application. The scope of protection shall be subject to the scope defined by the claims of this application.

Claims (18)

1. A battery comprises a positive pole piece, a diaphragm, a negative pole piece and electrolyte, and is characterized in that the positive pole piece and/or the negative pole piece comprises a current collector and an electrode active material layer formed on the surface of the current collector;

the current collector comprises an insulating layer and a conductive layer,

the insulating layer is used for bearing the conducting layer;

the conductive layer is used for bearing an electrode active material layer and is positioned on at least one surface of the insulating layer,

the conductive layer comprises a conductive layer body and a protective layer arranged on at least one surface of the conductive layer body, the protective layer is made of nickel oxide, and the normal-temperature thin-film resistor R of the conductive layer_SSatisfies the following conditions: r is more than or equal to 0.01 omega/□_S≤0.15Ω/□；

r represents the internal resistance of the battery, Cap represents the capacity of the battery, and the relationship between r and Cap satisfies:

25Ah·mΩ≤r×Cap≤400Ah·mΩ。

2. the battery of claim 1, wherein the conductive layer has a room temperature sheet resistance R_SSatisfies the following conditions: r is more than or equal to 0.02 omega/□_S≤0.1Ω/□。

3. The battery of claim 1, wherein the conductive layer has a thickness D2, D2 being: d2 is more than or equal to 300nm and less than or equal to 2 mu m.

4. The battery of claim 3, wherein 500nm ≦ D2 ≦ 1.5 μm.

5. The battery of claim 1, wherein the insulating layer has a thickness of D1, D1 satisfies: d1 is more than or equal to 1 mu m and less than or equal to 20 mu m.

6. The battery of claim 5, wherein 2 μm D1 μm 10 μm.

7. The battery of claim 6, wherein 2 μm D1 μm 6 μm.

8. The battery according to claim 1, wherein the conductive layer is made of at least one material selected from a metal conductive material and a carbon-based conductive material.

9. The battery according to claim 8, wherein the metal conductive material is at least one selected from the group consisting of aluminum, copper, nickel, titanium, silver, nickel-copper alloy, and aluminum-zirconium alloy, and the carbon-based conductive material is at least one selected from the group consisting of graphite, acetylene black, graphene, and carbon nanotubes.

10. The battery according to claim 1, wherein the insulating layer is made of at least one material selected from the group consisting of an organic polymer insulating material, an inorganic insulating material, and a composite material.

11. The battery according to claim 10, wherein the organic polymer insulating material is selected from at least one of polyamide, polyester terephthalate, polyimide, polyethylene, polypropylene, polystyrene, polyvinyl chloride, acrylonitrile-butadiene-styrene copolymer, polybutylene terephthalate, poly (paraphenylene terephthalamide), polypropylene, polyoxymethylene, epoxy resin, phenol resin, polytetrafluoroethylene, polyvinylidene fluoride, silicone rubber, polycarbonate;

the inorganic insulating material is selected from at least one of alumina, silicon carbide and silicon dioxide;

the composite material is at least one of epoxy resin glass fiber reinforced composite material and polyester resin glass fiber reinforced composite material.

12. The battery of claim 1, wherein the material of the conductive layer body is selected from at least one of a metal conductive material, a carbon-based conductive material; the metal conductive material is selected from at least one of aluminum, copper, nickel, titanium, silver, nickel-copper alloy and aluminum-zirconium alloy, and the carbon-based conductive material is selected from at least one of graphite, acetylene black, graphene and carbon nano tubes.

13. The battery of claim 1, wherein the protective layer is disposed only on a side of the conductive layer body facing away from the insulating layer, or the protective layer is disposed only on a side of the conductive layer body facing the insulating layer, or the protective layer is disposed on opposite surfaces of the conductive layer body.

14. The battery of claim 1, wherein the protective layer has a thickness of D3, D3 satisfies: d3 is not less than 1/10D2 and D3 is not less than 1nm and not more than 200 nm.

15. The battery of claim 14, wherein 10nm ≦ D3 ≦ 50 nm.

16. The battery of claim 1, wherein only the current collector forms a point break when the battery is subjected to an abnormal condition that induces a short circuit.

17. The battery of claim 16, wherein the current collector is a positive current collector.

18. The battery of claim 16, wherein the short circuit inducing abnormality is a nail.

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